海泡石-Al２Ｏ３混合载体对铂催化剂环己烷脱氢反应的影响

以三氧化二铝或海泡石(Sepiolite)-三氧化二铝混合物为载体,金属铂为活性组分,采用浸渍法分别制备了Pt／Ａl_２Ｏ_３、Pt／Ｓep-Ａl_２Ｏ_３催化剂,并考察了它们对环己烷脱氢反应的性能、抗硫性能及催化剂活性中心的影响。结果表明,Pt／Ｓep-Ａl_２Ｏ_３催化活性及抗硫性能均高于工业用Pt／Ａl_２Ｏ_３催化剂,同时增大了铂催化剂上的活性中心数及分散度。     

环己烷在碳化钼催化剂上的脱氢研究

以环己烷为碳源,采用程序升温还原法制备碳化钼催化剂,对前驱物和中间物及催化剂的晶相结构进行XRD表征,在固定床反应装置上进行环己烷的脱氢反应实验。固定反应压力为0.1 MPa,考察反应温度、空速、氢烃体积比和压力对碳化钼脱氢活性的影响。结果表明,催化剂活性相为高活性的β-Mo₂C,在反应温度450 ℃、空速2 h^-1、压力0.1 MPa和氢烃体积比200∶1条件下,环己烷转化率达88%,脱氢反应的选择性为79%。     

Modification of platinum-alumina catalysts. Effect of the addition of lithium to platinum in the dehydrogenation of cyclohexane

The modification of platinum-alumina catalysts by 0.1 wt% lithium does not affect to a large extent the dehydrogenating properties of platinum. However, when lithium is added to platinum through impregnation by nitrate salt in a higher content, residual nitrate species can remain on the catalyst surface, even after calcination at 773 K. These nitrate species can be coreduced with the platinum precursor and be associated to a significant sintering of the platinum particles.     

VOC deep oxidation over Pt catalysts using hydrophobic supports

The active hydrophobic-supported Pt catalysts were synthesized for VOC deep oxidation at low temperature (less than 200°C). The destruction of VOC could cost less at lower temperature due to less energy consumption. The advantage using hydrophobic support was that moistures from atmosphere and oxidation would not be adsorbed on the surface. Thus the active sites would not be cloaked and catalyst activity could be maintained, especially at low temperature. The hydrophobicity of supports was characterized by wetting angles. Porous SDB (styrene divinylbenzene copolymer) was found near 113°, indicating high hydrophobicity. Three Pt catalysts were prepared on SDB and activated carbons by incipient wetness method. Specific surface areas were measured by nitrogen adsorption. The thermal stability of SDB catalyst was examined by TGA, and found no degradation below 200°C in air. The surface compositions of catalysts were analyzed by EDS. XRD showed that Pt was well dispersed on supports after hydrogen reduction at 160°C. The chemical states of Pt were investigated by XPS, and suggested that the oxidized Pt^IV might be the active sites in the reaction. The deep oxidation of toluene/air mixture was carried out to test the activity of catalysts. Pt/SDB showed the highest activity among the catalysts and could completely oxidize 90 ppm toluene/air at VHSV=21 000 h⁻¹, 150°C. Redox mechanism was proposed to reveal the enhanced kinetic rates. The results suggested that the rate of toluene oxidation might be enhanced due to the fact that water, one of the products, was expelled from the hydrophobic surface.     

Sn掺杂量对Pt/Sn-MFI催化剂的丙烷脱氢性能影响

随着对丙烯需求的日渐增加,由丙烷催化脱氢制丙烯来实现对丙烯的增产,已成为增产丙烯的重要手段之一。利用水热法制备一系列不同Sn掺杂量的Sn-MFI载体,采用等体积浸渍法制备相同Pt负载量的Pt/Sn-MFI催化剂,通过XRD、N2吸附-脱附、FT-IR和H2-TPR等表征考察不同Sn掺杂量的催化剂对丙烷催化脱氢性能的影响。结果表明,Pt/Sn1. 3%-MFI催化剂具有最高的催化丙烷脱氢活性和稳定性,丙烷初始转化率为43. 3%,丙烯选择性为98. 9%。反应360 min后,丙烷转化率为25. 1%,选择性保持不变。     

Pt/Al_2O_3与Pt/MgO-Al_2O_3催化剂制备及其催化氢能载体甲基环己烷脱氢反应性能

以碱共沉淀法制备Mg-Al水滑石,然后采用浸渍法负载活性组分Pt,经焙烧、氢气还原得到Pt/Al_2O_3与Pt/Mg O-Al_2O_3催化剂,采用XRD、N2吸附-脱附、FT-IR、H2-TPR和Py-IR等分析Mg O的加入对Pt/Al_2O_3催化剂结构性能的影响,并在甲基环己烷连续脱氢反应中对比两种催化剂活性。结果表明,Pt/Mg O-Al_2O_3催化剂比表面积小于Pt/Al_2O_3催化剂,且表面基本无酸性活性中心,但表现出与Pt/Al_2O_3催化剂相同的脱氢活性。在Pt负载质量分数2%、催化剂用量0.5 g、甲基环己烷0.1 m L·min-1纯样进料和325℃反应10 h后,原料平均转化率79.9%,脱氢产物只有甲苯,对应的产氢速率192.8 mmol·(g-metal·min)-1,表现出优良的脱氢活性。     

负载型Pt-Fe/SiO_2催化剂催化环己烷一步氧化制己二酸

己二酸是合成尼龙-66和尼龙-46纤维的重要原料,并进一步用于生产许多重要的化工产品。工业上的己二酸多采用以硝酸为氧化剂的两步法合成,该工艺不仅工艺复杂,而且对设备有腐蚀作用,还会释放大量的温室气体N_2O。本文以负载型Pt/SiO_2、Fe/SiO_2和Pt-Fe/SiO_2为催化剂,采用过氧化氢和氧气为氧源,研究了环己烷一步氧化制己二酸的绿色合成路线。对催化剂进行ICP、BET比表面积、XRD、TEM等表征,结果表明,Pt-Fe/SiO_2催化剂中不存在与Pt或Fe对应的衍射峰。在最佳反应条件下,用高压釜进行了催化剂性能评价,结果表明,Pt-Fe/SiO_2催化活性略优于Pt/SiO_2和Fe/SiO_2。在环己烷转化率为28%的情况下,己二酸选择性达到33%。     

Production of hydrogen-rich gas via reforming of iso-octane over Ni–Mn and Rh–Ce bimetallic catalysts using spray pulsed reactor

The conversion of hydrocarbon fuels such as gasoline and diesel is a potential source for hydrogen production towards various fuel cell systems. A novel spray pulsed mode reactor to create alternate wet and dry conditions on the catalyst surface has been used in this study to enhance the rates of hydrogen production compared with the solid-gas phase reaction due to the improvement of the catalyst reactant contact. The production of hydrogen-rich gas by reforming of iso-octane (2,2,4-trimethylepentane) in the presence of steam and air has been studied at 600 and 700 °C over Ni–Mn and Rh–Ce bimetallic catalysts supported on alumina mesh. The feed rate of iso-octane was varied from 0.553 to 5.53 m mol min^–1 by controlling pulse injection in terms of the width and frequency of injection of iso-octane. Based on the product analysis optimized condition for higher hydrogen production and high H₂/CO ratio has been deduced.     

环己烷分子氧选择性氧化固体催化剂研究进展

对环己烷分子氧催化氧化制环己酮固体催化剂的最新进展进行了综述,重点介绍了贵金属催化剂、过渡金属及其氧化物催化剂和分子筛催化剂。指出锆基复合氧化物催化剂和负载在分子筛上的金催化剂具有较高的催化活性和选择性及好的稳定性,具有一定的应用及工业化前景。     

In situ hydrogen generation from cycloalkanes using a Pt/CNF catalyst

Pt catalyst supported on carbon nanofibers (CNFs) has been prepared via ion-exchange and it was characterized by XRD, TEM, N₂ physisorption and CO chemisorption. The Pt/CNF catalyst has a small Pt crystallite size in the range of 2–3 nm. This catalyst has been tested in the dehydrogenation of decalin, which is a cycloalkane proposed in the literature as H₂ storage media for vehicles and portable devices. The objective is finding a Pt catalyst suitable for in situ generation of H₂ from chemical storage in decalin. The results revealed that Pt supported on CNF outperforms a Pt catalyst supported on micro–mesoporous activated carbon. Finally, we propose a reactor configuration aiming at the intensification of H₂ production in continuous.     

正构生物烷烃在Pt/ZSM-5催化剂上选择性加氢裂化制备液体生物燃料

开发了一种通过正构生物烷烃在Pt/ZSM-5催化剂上的选择性加氢裂化来制备高品质液体生物燃料的新方法.生产得到的液体生物燃料包含了煤油、汽油和柴油,分离后可直接作为航空燃料或车用燃料使用.以商业ZSM-5分子筛为载体,制备和表征了不同组成的Pt/ZSM-5催化剂.采用转化率、煤汽比和异构率为指标,考察了温度、压力和空速等条件对反应的影响,比较了不同组成时催化剂的催化性能.结果表明:对于同一催化剂,裂化产物异构率随转化率增加而增加;除转化率外,异构率还与酸性位的烯烃被覆度相关;当采用0.7%Pt/ZSM-5(硅铝比50)为催化剂时,在4MPa、320℃、1h^-1、氢油体积比1500:1的反应条件下,原料转化率即可达到82%,产物中煤油含量为43.6%,异构率为1.29,汽油含量为38.0%.     

Ｐｔ／Ｃ催化剂催化硝基苯加氢制对氨基苯酚工艺过程剖析

本文介绍了硝基苯催化加氢制对氨基苯酚的研究概况;探讨了在加氢工艺路线中的若干技术关键,如温度、氢分压、ｐＨ值及加氢深度等;评述了添加助剂提高对氨基苯酚收率的方法,并对其优缺点进行了讨论。     

Pt/TiO_2催化二甲醚部分氧化重整制氢

二甲醚是一种理想的氢载体,可用于解决氢的储存和运输。以Pt/TiO_2为部分氧化催化剂,结合Ni/Al_2O_3重整催化剂,考察钛前驱体和焙烧温度对二甲醚部分氧化重整制氢反应的影响。结果表明,以Ti(C4H9O)4为原料制备的TiO_2为金红石相,Ti(SO4)2或Ti O(OH)2为原料制备的TiO_2为锐钛矿相;以Ti(C4H9O)4为原料制备的Pt/TiO_2-E催化剂催化性能略好,转化率接近100%,H2收率约90%,表明金红石相TiO_2负载的Pt催化剂略佳;以Ti(SO4)2为原料制备的Pt/TiO_2-S催化剂500℃焙烧可获得金红石相TiO_2。与Pt/Al_2O_3催化剂相比,Pt/TiO_2催化剂具有更好的催化性能,H2收率超过90%,而Pt/Al_2O_3催化剂H2收率约80%。     

Hydrogenative ring opening of propylcyclopropane over silica-supported Pt and Pd catalysts

The effects of temperature and hydrogen pressure on the hydrogenative ring opening of propylcyclopropane over Pt/SiO₂ and Pd/SiO₂ catalysts were studied. Temperature dependence in the 323–373 K temperature range in a pulse system was investigated, while a static recirculation reactor was used for hydrogen pressure dependence measurements. The ring-opening reactions took place exclusively at all temperatures and hydrogen pressures studied. Monotonous increase was observed for the reactivity of propylcyclopropane as a function of temperature. At constant temperature, the reaction rate vs. hydrogen pressure dependence curves passed through a maximum indicating dissociative adsorption over both Pt and Pd catalysts. The scission of the sterically less hindered direction (producing 2-methylpentane) was the major reaction pathway on both catalysts with practically identical regioselectivity values. On the basis of these results aselective mechanism was proposed for the ring-opening reaction.     

Adsorption and reactions of ethanol and ethanol–water mixture on alumina-supported Pt catalysts

The formation of surface species in the ethanol–water interaction and the reforming of ethanol have been investigated on Pt/Al₂O₃ catalysts and for comparison on the support. By means of infrared spectroscopy it was found that on Pt/Al₂O₃ not only adsorbed ethanol, different types of ethoxy species but also traces of acetaldehyde and a significant amount of acetate groups were detectable on the surface. The latter species were stable even at 700 K. The gas phase analysis of the ethanol-dosed surface showed at higher temperature considerable amount of ethylene in the case of Al₂O₃ and hydrogen in the case of Pt/Al₂O₃.

In the ethanol + water reaction the selectivity of H₂ and CO₂ formation at 723 K decreased in time, while that of ethylene increased. This trend was attenuated by increasing the following parameters: water concentration, metal loading and reaction temperature. It was assumed that this behavior of Pt/Al₂O₃ in the ethanol + water reaction can be attributed to the formation of surface acetate groups which hindered the reaction on the metal, although these species were located rather on the support.     

Oxidation of carbon black over various Pt/MOx/SiC catalysts

Catalytic activities of various Pt/MO_x/SiC systems for carbon oxidation under simulated diesel exhaust gas were investigated in temperature-programmed reactions. When Pt/MO_x (MO_x=TiO₂, ZrO₂, Al₂O₃) was loaded onto silicon carbide (SiC), the oxidation activities became higher than those of Pt/MO_x alone or other Pt/MO_x/SiC systems (MO_x=Ta₂O₅, WO₃, Nb₂O₅, SnO₂, SiO₂, CeO₂, MoO₃, V₂O₅). Among them, Pt/TiO₂/SiC exhibited the highest activity. We discuss the activity of MO_x=TiO₂, ZrO₂, and Al₂O₃ in connection with NO oxidation activity, adsorption of sulfate onto the support, Pt dispersion, and specific surface area of the catalyst. Furthermore, we investigated the catalytic performance of Pt/TiO₂/SiC in more detail under isothermal conditions and in a staged arrangement.     

Catalytic and electrocatalytic production of H2 from propane decomposition over Pt and Pd in a proton-conducting membrane-reactor

In the present study, the C₃H₈ decomposition reaction is studied in a double-chamber proton-conducting cell-reactor. The proton conductor was a strontia–ceria–ytterbia perovskite disk of the form: SrCe_0.95Yb_0.05O₃₋. The working electrode-catalyst was either Pt or Pd, in the form of a polycrystalline film. The reaction temperature varied between 923 and 1023 K and the partial pressure of propane in the feed gas was 2 kPa. The hydrogen produced by the reaction was electrochemically transported through the walls of the proton-conducting disk, to the outer reactor-chamber. The two electrodes (Pt and Pd) are compared in terms of their catalytic and electrocatalytic activities.     

FeM双金属用于甲烷催化裂解制纯氢气和碳纳米材料

采用熔融法以铁、钼、铜和钨硝酸盐为原料,制备出一系列的Fe_xM_y（M=Mo、Cu、W）双金属催化剂。首先考察了一系列的Fe₁₅M₁（M=Mo、Cu、W）双金属催化剂的甲烷催化裂解（CDM）活性,Fe₁₅Mo₁的催化活性远高于Fe₁₅Cu₁和Fe₁₅W₁。通过比表面积测试（BET）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）和拉曼光谱（Raman）等分析方法对Fe₁₅M₁的物理特性、结构组成、还原特性和副产物碳纳米材料（CNMs）的石墨化度等进行表征。进一步考察了金属Mo的掺杂量和焙烧温度对Fe_xMo_y双金属催化剂的甲烷转化率和碳产率的影响。Fe₁Mo₁表现出优异的催化性能,其碳产率（6g_C/g_cat）高于纯Fe的碳产率（4.35g_C/g_cat）。XRD和X射线光电子能谱（XPS）分析表明,Fe₁Mo₁双金属形成Fe₂(MoO₄)₃相,提高了其催化活性和稳定性;透射电镜（TEM）结果表明,Fe₁Mo₁催化剂CDM反应后的CNMs为竹节状的碳纳米管。     

H2 production through steam reforming of ethanol over Pt/ZrO2, Pt/CeO2 and Pt/CeZrO2 catalysts

The effect of the support nature and metal dispersion on the performance of Pt catalysts during steam reforming of ethanol was studied. H₂ and CO production was facilitated over Pt/CeO₂ and Pt/CeZrO₂, whereas the acetaldehyde and ethene formation was favored on Pt/ZrO₂. According to the reaction mechanism, determined by temperature-programmed desorption (TPD) and Diffuse Reflectance Infrared Spectroscopy (DRIFTS) analysis, some reaction pathways are favored depending on the support nature, which can explain the differences observed on the resulting product distribution.